Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Prepare the vegetables by halving the baby potatoes, slicing the carrots into half-inch rounds, and cutting the broccoli into bite-sized florets.
Roughly chop the red onion into large chunks and finely mince the garlic cloves.
Place the chicken breast in the center of the sheet pan and surround it with the potatoes, carrots, broccoli, and onion.
Drizzle the olive oil evenly over the chicken and vegetables, then sprinkle with the minced garlic, rosemary, thyme, sea salt, and black pepper.
Use your hands or tongs to toss the vegetables and coat the chicken thoroughly in the oil and herb mixture.
Spread everything into a single layer, ensuring the vegetables aren't overcrowded so they roast rather than steam.
Roast in the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are fork-tender.
Remove from the oven and let the chicken rest for 5 minutes before slicing to ensure the juices remain locked in.